Claudiu Treaba

The contour electrode array: safety study and initial patient trials of a new perimodiolar design.

Objective The aim of these studies was to investigate the insertion properties and safety of a new intracochlear perimodiolar electrode array design (Contour). Background An electrode array positioned close to the neural elements could be expected to reduce stimulation thresholds and might potentially reduce channel interaction. Methods Two sequential studies were conducted. In study 1, the Contour electrode array was inserted in 12 human temporal bones. After cochlear surface preparation, the position of the array was noted and the basilar membrane was examined for insertion damage. On the basis of the outcome of this temporal bone study, study 2 investigated the Contour array, mounted on a Nucleus CI-24 M device and implanted in three adult patients. Results Study 1 showed that in 10 temporal bones, the Contour array was positioned close to the modiolus, and the basilar membrane was intact. In the two remaining bones, the arrays had pierced the basilar membrane and were positioned in the scala vestibuli apical to the penetration. Statistical analysis showed an equivalent probability of insertion-induced damage of the two array designs. In study 2, image analysis indicated that the Contour electrodes were positioned closer to the modiolus than the standard Nucleus straight array. Lower T and C levels, but higher impedance values, were recorded from electrodes close to the modiolus. Initial speech perception data showed that all patients gained useful open-set speech perception, two patients achieving scores of 100% on sentence material 3 months postoperatively. Conclusions The temporal bone studies showed the Contour electrode array to be generally positioned closer to the modiolus than the standard Nucleus straight array, and to have an equivalent probability of causing insertion-induced damage.

Comparison of electrode position in the human cochlea using various perimodiolar electrode arrays

OBJECTIVE This study was conducted to evaluate the insertion properties and intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard Cochlear/Melbourne array. BACKGROUND Advantages to be expected of a perimodiolar electrode array include both a reduction in stimulus thresholds and an increase in dynamic range, resulting in a more localized stimulation pattern of the spiral ganglion cells, reduced power consumption, and, therefore, longer speech processor battery life. METHODS The test arrays were implanted into human temporal bones. Image analysis was performed on a radiograph taken after the insertion. The cochleas were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed for position of the electrode array as well as insertion-related intracochlear damage. RESULTS All perimodiolar electrode arrays were inserted deeper and showed trajectories that were generally closer to the modiolus compared with the standard electrode array. However, although the precurved array designs did not show significant insertion trauma, the method of insertion needed improvement. After insertion of the straight electrode array with positioner, signs of severe insertion trauma in the majority of implanted cochleas were found. CONCLUSIONS Although it was possible to position the electrode arrays close to the modiolus, none of the three perimodiolar designs investigated fulfilled satisfactorily all three criteria of being easy, safe, and atraumatic to implant.

The temporalis pocket technique for cochlear implantation: an anatomic and clinical study.

Objective: To describe the surgical anatomy and clinical outcomes of a technique for securing cochlear implant receiver/stimulators (R/S). Receiver/stimulators are generally secured by drilling a custom-fit seat and suture-retaining holes in the skull. However, rare intracranial complications and R/S migration have been reported with this standard method. Newer R/S designs feature a low profile and larger, rigid flat bottoms in which drilling a seat may be less appropriate. We report a technique for securing the R/S without drilling bone. Study Design: Anatomic: Forty-eight half-heads were studied. Digital photography and morphometric analysis demonstrated anatomic boundaries of the subpericranial pocket (t-pocket). Clinical: Retrospective series of 227 consecutive Cochlear implant recipients implanted during a 2-year period using either the t-pocket or standard technique. The main outcome measures were rates of R/S migration and intracranial complications. Minimum follow-up was 12 months. Results: The t-pocket is limited anteriorly by dense condensations of pericranium anteriorly at the temporal-parietal suture, posteroinferiorly at the lamdoid suture, and anteroinferiorly by the bony ridge of the squamous suture. One hundred seventy-one subjects were implanted using the t-pocket technique and 56 using the standard technique, with a minimum follow-up of 12 months. There were no cases of migration or intracranial complications in either group. Conclusion: The t-pocket secures the R/S with anatomically consistent strong points of fixation while precluding dural complications. There were no cases of migration or intracranial complication noted. Further trials and device-specific training with this technique are necessary before it is widely adopted.

High-resolution cone-beam computed tomography: a potential tool to improve atraumatic electrode design and position.

Abstract Conclusions: Flat-panel cone-beam computed tomography (CBCT) is able to assess the trajectory of the implanted cochlear implant (CI) array. This is essential to determine specific effects of electrode design and surgical innovations on outcomes in cochlear implantation. CBCT is a non-invasive approach yielding similar data to histopathological analyses, with encouraging potential for use in surgical, clinical and research settings. Objectives: To examine the fidelity of CBCT imaging and custom 3D visualization in characterizing CI insertion in comparison to gold standard, histopathological examination. Methods: Eleven human temporal bones were implanted with the ‘Straight Research Array’ (SRA). Post-insertion, they were imaged with a prototype mobile C-arm for intraoperative CBCT. Post-acquisition processing of low-dose CBCT images produced high-resolution 3D volumes with sub-millimetre spatial resolution (isotropic 0.2 mm3 voxels). The bones were resin impregnated and sectioned for light microscopic examination. Dimensional electrode characteristics visible in section images were compared with corresponding CBCT images by independent observers. Results: Overall, CBCT demonstrated adequate resolution to detect: 1) scala implanted; 2) kinking; 3) number of intracochlear contacts; 4) appropriate ascension of the array; and overall confirms ideal insertion. CBCT did not demonstrate adequate resolution to detect reversal of electrode contacts or basilar membrane rupture.

Does cochleostomy location influence electrode trajectory and intracochlear trauma

Trauma to intracochlear structures during cochlear implant insertion is associated with poorer hearing outcomes. One way surgeons can influence insertion trauma is by choosing the surgical approach. We seek to compare cochleostomy (CO), peri–round window (PRW), and round window (RW) approaches using a fresh frozen temporal bone model.

Real-time measurement of electrode impedance during intracochlear electrode insertion.

This pilot study details the use of a software tool that uses continuous impedance measurement during electrode insertion, with the eventual potential to assess and optimize electrode position and reduce insertional trauma.

Electrode insertion mechanics and outer wall forces with the Nucleus 24 Contour Advance™ electrode

Modiolus hugging gave a small but significant reduction of spread of neural excitation on the basal and apical apart of the Nucleus CI24R(CS) cochlear implant. There was no significant effect on the mid-section of the implant array. To our knowledge, our results are the first within-subject demonstration of the effect of modiolus hugging. Our intra-operative measurements had to be performed at a high stimulus level. At lower stimulation levels, closer to those an implant user would typically use, the reduction of the spread of excitation may be more pronounced, as is also suggested by Cohen et al. (2003). We conclude that modiolus hugging improves stimulation selectivity. This may improve speech discrimination and be beneficial for implant users.